Rapid drying moisture cured coatings

ABSTRACT

Fast drying (curing) polyurethane coatings with excellent physical properties may be made from an isocyanate, a polyhydric alcohol and a polyol which is a condensation product of glyoxal and a polyhydric alcohol which may also contain monofunctional alcohols and residues of vinyl carboxylic acids. Such coatings cure both by reaction with air and moisture. Polyurethane coatings are useful anywhere a tough covering is required. For example, the coatings are useful in flooring, roofing, and wire covering.

United States Patent Schulze et al.

[54] RAPID DRYING MOISTURE CURED COATINGS [72] Inventors: Heinz Schulze,6408 Wilbur Drive, Austin, Tex. 78757; Michael Cuscurida, 301 E. 34 St.,Austin, Tex. 78705 [22], Filed: Sept. 28,1970

[21] Appl. No.: 76,329

[56] References Cited UNITED STATES PATENTS 3,533,972 10/1970 Pawlak etal. ..260l77.5 AP 3,557,249 1/1971 Dannels et al. .....260/77.5 AP3,054,803 9/1962 Robeson et al. ....260/77.5 AP

FOREIGN PATENTS 0R APPLICATIONS 580,469 9/1946 Great Britain [451 Sept.12, 1972 842,075 6/1952 Germany OTHER PUBLICATIONS Head, J. Chem. 800.,1955, pp. 1036- 1037 Raudnitz, Chem. & lnd., 1956, p. 166

Rodd (ED.), Chemistry of Carbon Compounds," IA, Elsevier, N.Y., 1951, p.715

Primary Examiner-Donald E. Czaja Assistant Examiner-M. J. WelshAttorney-John R. Kirk, In, H. G. Jackson and Terrence D. Dreyer [57]ABSTRACT Fast drying (curing) polyurethane coatings with excellentphysical properties may be made from an isocyanate, a polyhydric alcoholand a polyol which is a condensation product of glyoxal and a polyhydricalcohol which may also contain monofunctional alcohols and residues ofvinyl carboxylic acids. Such coatings cure both by reaction with air andmoisture.

Polyurethane coatings are useful anywhere a tough covering is required.For example, the coatings are useful in flooring, roofing, and wirecovering.

10 Claims, No Drawings v l 1 RAPID DRYING MOISTURE CURED COATINGSBACKGROUND OF THE INVENTION moisture cured coatings may befound inSaunders, J.

H. and Frisch,K. C., Polyurethanes: Chemistry and Technology, Part IITechnology, lnterscience, New York, 1964.- In general, prior artmoisture cured coatings are made by reacting a conventional polyol withan excess of isocyanate, applying this liquid to a surface, and allowingthe resultant coating to cure in the-open air byreaction of the excessof isocyanate groups with moisture in the air; The conventional polyolsare most often simply polyhydric alcohols. Diols-suclias 1,3 butane dioll,5 pentane" diols, and polypropylene glycols of various molecularweights are co'r'nmor'rly used. Triols, such as trimethylolpropane,

glycerine,and alkylene oxide adducts ofthe above are also used in-;priorart moisture cured coatings. Although acceptable coatings'may'beobtained using these conventional polyhydricalcohols polyols,

there are"disadvantages. The principle disadvantage connected with priorart coating is excessive cure or drying time. It is a definite advantageto have a coating which will cure rapidly. As the liquid coating isapplied it begins the process of reacting with moisture in the air andbecomes more viscous until it hardens and loses any sticky (tacky),quality. Rapid curing means rapid hardening andaids in the minimizationof dust collection 'on' the coating, eases processing problems bydecreasing the cycle time and, prevents excessive running on inclinedsurfaces. The hardness of prior art coatings could be adjusted byvarying the molecular weight and functionalityof the conventional polyolor polyols used. In general the lower the molecular weight and thehigher the average functionality of the polyols, the harder the finishedcoating. However, increased hardness most often'resulted in increasedbrittleness of the coating. This lack of flexibility resulted incracking under heavy use. I

It has been surprisingly discovered that the use of the new polyols ofthis invention in coating formulations also containing conventionalpolyols imparts rapid curing without detracting from other desirableproperties of the coatings. The new polyols enable the coatings to cureboth by reaction with moisture and air.

Also, by using the polyols of this invention in addition toconventionalpolyols in a coating formulation a very hard coating may be made whichremains flexible.

The preparation of condensation products of glyoxal and triols isdisclosed in German Pat. No. 842,075. The use of these materials aspolyols in polyurethane coatings is not disclosed in the prior art.

SUMMARY OF THE INVENTION This invention is a new class of polyurethanemoisture cured coatings which may be made by the reaction of an excessof polyisocyanates with hydroxycontaining materials which reactionproduct is then applied in a thin film or coating and allowed to cure bythe reaction with air and moisture in the air. The invention is also amethod for making the coatings. The invention is also a portion of thehydroxy containing materials (polyols) employed in the coatings. Theseare made by the reaction of glyoxal'and a polyhydric alcohol in suchproportion that the resultant polyol has at least two hydroxyl groupsavailable for the urethane reaction; the reaction of glyoxal and apolyhydric alcohol and a monofunctional allylic alcohol in suchproportion that the resultant polyol has at least an average of 0.5hydroxyl groups available for the urethane reaction; or the reaction ofglyoxal and a polyhydric alcohol and a monofunctional vinyl carboxylicacid in such proportion that the resultant polyol has at least anaverage of 0.5 hydroxyl groups available for the urethane reaction. Theremaining hydroxy containing materials necessary for the coatingformulations are conventional polyols. i

DESCRIPTION OF PREFERRED. EMBODIMENTS v The polyolsof our inventioninclude the reaction product of glyoxal and a polyhydric 'alcohol;.thereaction product of glyoxal and a polyhydric alcohol and amonofunctional allylic alcohol; and the reaction product of glyoxal anda polyhydric alcohol and a monofunctional vinyl carboxylic acid. 1 I

Examples of polyfunctional alcohols useful in the process of ourinventioninclude, for 7 example, glycerine, trimethylolpropane, 1,2,6hexanetriol, polypropylene glycols of various molecular weights andalkylene oxide adducts of polyfunctional alcohols. Any polyfunctionalalcohol which will react with glyoxal is within the scope of ourinvention.

The monofunctional alcohols which maybe reacted with the glyoxal andpolyfunctional alcohols are preferably those containing an allylicgroup. The allylic group aids in the rapid curing properties of theprocess of our invention. Examples of such monofunctional alcohols areallyl alcohol, crotyl alcohol or higher allylic alcohols as for instancethose obtained by allylic halogenation and subsequent hydrolysis ofolefins. Likewise, the vinyl carboxylic acids which may be reacted withthe glyoxal and polyfunctional alcohols are preferably those containingan unsaturated group. Examples of such acids are acrylic, methacrylicand crotonic acid.

In addition to the polyols of the invention, conventional polyols arealso a necessary ingredient in the coatings of the invention. Theseconventional polyols are most often simply polyhydric alcohols. Diolssuch as 1,3 butane diol, 1,5 pentane diol, and polypropylene glycols ofvarious molecular weights are examples of commonly used conventionalpolyols. Further examples of conventional polyols are triols such astrimethylolpropane, glycerine, and alkylene oxide adducts of the above.

In order to form polyurethane coatings using the conventional polyolsand the polyols of the invention prepared as above described, anotheringredient is essential: an isocyanate. An isocyanate reacts directlywith the active hydrogens of the polyols. The isocyanate may bealiphatic or aromatic. The isocyanate may be difunctional such astoluene diisocyanate or a polyfunctional polyaryl isocyanate, asproduced by the phosgenation of the reaction product of aniline andformaldehyde. Such reactions are well known and described in US. Pat.Nos. 2,683,730, 3,277,173, 3,344,162 and 3,362,979, for example. Thepolyaryl isocyanates thus formed have functionalities greater than twowhich can be varied up to the higher functional materials. In practice,however, functionalities greater than four are attained only withdifficulty. However, for purposes of practice of my invention, materialswith a functionality as high as five may be used. It is preferred thatthe functionality be from two to about four, and especially preferredthat the functionality of the polyaryl isocyanate used in the practiceof my invention be from about 2.3 to about 3.5.

The especially preferred isocyanate for use in the process of ourinvention is toluene diisocyanate.

Although coatings may be prepared without using catalysts, it issometimes desirable to use either a tertiary amine or an organic metalsalt in the formulation to catalyze the reaction between the freeisocyanate groups and the moisture in the air.

Many useful catalyst materials for the urethane reaction are well knownand may be employed in the practice of the invention. Examples ofsuitable tertiary amines, used either individually or in mixture, arethe N-alkylmorpholines, N-alkylalkanolamines,N,N-dialkylcyclohexylamines and alkylamines where the alkyl groups aremethyl, ethyl, propyl, butyl, etc. Also tn'ethylenediamine,tetramethylethylenediamine, triethylamine, tripropylamine,tributylamine, triamylarnine, pyridine, quiniline, dimethylpiperazine,dimethylhexylhexahydroaniline, piperazine, N-ethylmorpholine,2-methy1piperazine, dimethylaniline and nicotine, for example, areuseful urethane catalysts. Also, useful catalyst are organo-metalliccompounds including those of bismuth, lead, tin, titanium, iron,antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc,nickel, serium, molybdenum, vanadium, copper, manganese, zirconium, etc.Some examples of these metal catalysts included bismuth nitrate, lead2-ethylhexoate, lead benzoate, lead oleate, tributyltin, butyltintrichlorite, stannic chloride, stannous octoate, stannous oleate, ferricchloride, antimony trichloride, antimony glycolate, tin glycolates, etc.Selection of the individual catalysts and proportions to use in thepolyurethane reaction are well within the knowledge of those skilled inthe art, and an amine and organo metallic compound are often usedtogether in the polyurethane reaction.

A solvent must also be used in the coating before it is applied to aidin application, viscosity adjustment or storage stability. The solventshould be inert to the reaction of the glyoxal with the alcohols andcarboxylic acids, inert to the reaction of the isocyanates with hydroxylgroups and inert to the isocyanate groups. Examples of suitable solventsare xylene, 2-ethoxyethylacetate, ethyl benzene, toluene, mineralspirits, ethyl acetate, cyclohexanone, methyl ethyl ketone, and arnylacetate.

The following examples will illustrate the preparation of glyoxal-polyolcondensation products and their application and usefulness inpolyurethane coatings.

EXAMPLE 1 This example will illustrate the preparation of aglycerine-glyoxal condensate.

A mixture of glycerine (920 g., 10 moles), 40 percent glyoxal (725 g.,5.0 moles), (50 g.) of an acid ionexchange resin, and toluene (500 ml.)was subjected to an azeotropic distillation until 64 g. of an aqueousphase were separated. After cooling, the toluene phase was decanted andthe residue diluted with dioxane (500 ml.). It was then filtered warmand stripped at C./0.1 mm. The light brown, viscous residue (957 g.) hada hydroxyl number of 483 and a number average molecular weight of 270.

EXAMPLE 2 This example will illustrate the preparation of aglycerine-glyoxal-allyl alcohol condensate.

A mixture of glycerine (460 g., 5 moles), 40 percent glyoxal (725 g.,5.0 moles), allyl alcohol (1,400 ml., 20.6 moles), benzene (1,400 ml.),and an acid ionexchange resin (50 g.) was heated under reflux (72-84 C.)for 16 hours. An aqueous phase (749 g. containing 14.8 percent allylalcohol) was separated by azeotropic distillation through a 50 mm.packed column.

The reaction mixture was filtered and stripped at 100 C. under aspiratorvacuum, refiltered and finally dried at 35 C./0.l mm. The pale yellowreaction product was of low viscosity and was water insoluble. It had ahydroxyl number of 164, iodine number of 190, and a number averagemolecular weight of 266.

EXAMPLE 3 This example will illustrate the preparation of a1,2,6-hexanetriol-glyoxal-allyl alcohol condensate.

A mixture of 1,2,6-hexanetriol (420 g., 3 moles), 40 percent glyoxal(402 g., 3 moles), allyl alcohol (696 g., 11.2 moles), benzene (600ml.), and an acid ion exchange resin was heated to boiling and theaqueous layer removed. When water formation ceased, benzene and excessallyl alcohol were removed to a pot temperature of 87 C. The mixture wasthen heated to C. under aspirator vacuum and then under full vacuum to apot temperature of 100 C. The product weighed 695 g. and had a hydroxylnumber of 218.

EXAMPLE 4 This example illustrates the superior coating formulationusing the polyols of our invention along with conventional polyols incoating formulations. The propylene oxide adduct of glycerine, thepolypropylene glycol and trimethylolpropane are conventional polyols.The glyoxal containing materials are polyols of the invention. Thedibutyltin dilaurate is a catalyst. The xylene and 2-ethoxyethyl acetateare solvents. The di-tbutyl p-cresol is an oxidation inhibitor.

Run A, B, and C are coatings made with the polyols of our invention aspart of the formulation. Run D is a typical prior art coatingformulation. Note the improvement in tack-free time of Runs A, B, and Cas compared to D and also the superior elongation of A, B, and C ascompared to D. Run E illustrates that just the addition of allyl groups(tetra allyl oxyethane) to a prior art formulation does not acceleratedrying. The coating of Run E had an excessively long tack-free time andwas also soft. The allyl groups must be incorporated into the polymernetwork as in Runs A, B, and C in order to facilitate fast curing.

,Di-t-butyl p-cresol Tack-free time is measured according to the methodOutlined in US. Pat. No. 2,406,989. The Pencil hard- 4 Formulation, pbw.Propylene oxide adduct of glycerine- 260 molecular weightGlycerine-glyoxal condensate Glycerine-glyoxal-allyl alcohol condensate1,2,6-Hexanetriolglyoxal-allyl alcohol condensate TrimethylolpropaneTetrallyloxyethane Polypropylene glycol- 2000 molecular weightDibutyltin dilaurate Toluene diisocyanate Xylene Z-Ethoxyethylacetateisocyanate to hydroxyl ratio Film properties Tack-free time,

(min.)'

Pencil hardness Impact resistance, in.

Pass I60 Pass 160 3860 Pass Pass Pass Pass I60 160 Forward Reverse zsoous Tensile, psi.

Elongation,

Taber Wear Factor, CS-10, 1000 g., 1000 cycles, mgrn. loss 38.9 37.8 .33ass "4 mil wet film thickness Iclaim: g

1. In a urethane coating composition made by reacting an isocyanate withconventional polyols the improvement which comprises using an additionalpolyol made by the condensation reaction, with removal of water, ofglyoxal and a polyhydric alcohol wherein the additional polyol containsat least two hydroxyl groups available for the urethane reaction.

2. A coating composition according to claim 1 wherein the isocyanate istoluene diisocyanate.

3. In a urethane coating composition made by reacting an isocyanate withconventional polyols the improvement which comprises using an additionalpolyol made by the condensation reaction, in the presence of an acid ionexchange resin, with removal of water, of glyoxal, a polyhydric alcohol,and a monofunctional allylic alcohol wherein the additional polyolcontains at least an average of 0.5 hydroxyl groups available for theurethane reaction.

4. A coating composition according to claim 3 wherein the isocyanate istoluene diisocyanate and the monofunctional allylic alcohol is allylalcohol.

5. In a urethane coating composition made by reacting an isocyanate withconventional polyols the improvement which comprises using an additionalpolyol made by the condensation reaction, in the presence of an acid ionexchange resin, with removal of water, of glyoxal, a polyhydric alcohol,and a monofunctional vinyl carboxylic acid wherein the additional polyolcontains at least an average of 0.5 hydroxyl groups available for theurethane reaction. v

6. A method for preparing a polyurethane surface coating whichcomprises 1. mixing and reacting, in the presence of an inert solvent,an excess of isocyanate with a mixture of a conventional polyol, and anadditional polyol having at least two hydroxyl groups available for theurethane reaction and prepared by a. mixing and reacting in acondensation reaction glyoxal and a polyhydric alcohol in the presenceof a solvent; b. removing water from saidreaction; and c. recoveringsaid additional polyol from the reaction mixture; I '1 applying saidisocyanate reaction product to a surface; and

curing said polyurethane coating by allowing the excess isocyanate toreact with moisture in air.

7. A method according to claim 6 wherein the isocyanate is toluenediisocyanate- 8. A method for preparing a polyurethane surface coatingwhich comprises 1. mixing and reacting, in the presence of an inertsolvent, an excess of isocyanate with a mixture of a conventional polyoland an additional polyol having at least an average of 0.5 hydroxylgroups available for the urethane reaction and prepared a. mixing andreacting in a condensation reaction glyoxal, a polyhydric alcohol and amonofunctional allylic alcohol in the presence of a solvent and an acidion'exchange resin;

1). refluxing said reaction mixture and removing water from saidreaction; and

c. recovering said additional polyol from the reaction mixture;

2. applying said isocyanate reaction product to a surface; and

3. covering said polyurethane coating by allowing the excess isocyanateto react with moisture in air.

9. A method according to claim 8 wherein the isocyanate is toluenediisocyanate and the monofunctional allylic alcohol is allyl alcohol.

10. A method for preparing a polyurethane surface coating whichcomprises 1. mixing and reacting, in the presence of an inert solvent,an excess of isocyanate with a mixture of a conventional polyol and anadditional polyol having at least an average of 0.5 hydroxyl groupsavailable for the urethane reaction and prepared a. mixing and reactingin a condensation reaction glyoxal, a polyhydric alcohol and amonofunctional vinyl carboxylic acid in the presence of a solvent and anacid ion exchange resin;

b. refluxing said reaction mixture and removing water from saidreaction; and

c. recovering said additional polyol from the reaction mixture; 2.applying said isocyanate reaction product to a surface; and 3. coveringsaid polyurethane coating by allowing the excess isocyanate to reactwith moisture in air.

2. A coating composition according to claim 1 wherein the isocyanate istoluene diisocyanate.
 2. applyinG said isocyanate reaction product to asurface; and
 2. applying said isocyanate reaction product to a surface;and
 2. applying said isocyanate reaction product to a surface; and 3.covering said polyurethane coating by allowing the excess isocyanate toreact with moisture in air.
 3. covering said polyurethane coating byallowing the excess isocyanate to react with moisture in air.
 3. curingsaid polyurethane coating by allowing the excess isocyanate to reactwith moisture in air.
 3. In a urethane coating composition made byreacting an isocyanate with conventional polyols the improvement whichcomprises using an additional polyol made by the condensation reaction,in the presence of an acid ion exchange resin, with removal of water, ofglyoxal, a polyhydric alcohol, and a monofunctional allylic alcoholwherein the additional polyol contains at least an average of 0.5hydroxyl groups available for the urethane reaction.
 4. A coatingcomposition according to claim 3 wherein the isocyanate is toluenediisocyanate and the monofunctional allylic alcohol is allyl alcohol. 5.In a urethane coating composition made by reacting an isocyanate withconventional polyols the improvement which comprises using an additionalpolyol made by the condensation reaction, in the presence of an acid ionexchange resin, with removal of water, of glyoxal, a polyhydric alcohol,and a monofunctional vinyl carboxylic acid wherein the additional polyolcontains at least an average of 0.5 hydroxyl groups available for theurethane reaction.
 6. A method for preparing a polyurethane surfacecoating which comprises
 7. A method according to claim 6 wherein theisocyanate is toluene diisocyanate.
 8. A method for preparing apolyurethane surface coating which comprises
 9. A method according toclaim 8 wherein the isocyanate is toluene diisocyanate and themonofunctional allylic alcohol is allyl alcohol.
 10. A method forpreparing a polyurethane surface coating which comprises